Right On. I am using the 16C54 oscillator to drive a second PIC in some product versions, and another small board in still another version. The extra traces provide all the pf needed for C2. Omitting C2 cap nearly triples the oscillator pp voltage on the scope, and makes it very resistant to quenching (by touching with finger, eg.). With C2 = 22 pf, the osc was weak at best. Thought I would pass this observation along FWIW. Thanks. -----Original Message----- From: Russell McMahon [SMTP:apptech@CLEAR.NET.NZ] Sent: Wednesday, October 08, 1997 3:23 AM To: PICLIST@MITVMA.MIT.EDU Subject: Re: Oscillator, PIC16C54 > John Shreffler writes - > About 5% of my production run is having > problems with start up of the oscillator. I am > using a 4 MHz parallel crystal Digikey part number > X006-ND, with a pair of 22pf NPO ceramic chips > on either side to ground. Local bypass is good. Microchip have a FAQ on the PIC oscillator covering this question. It was at www.microchip2.com/techsup/faq/faqosc.htm on 20 Feb this year. In summary: - Check clock mode is the correct one - Power via an I/O pin before power on could cause this as could slow power supply rise time etc. ((A brown out protection circuit is always a good idea)). - Having C2 higher than C1 can help. - Other values than suggested in the data book may be appropriate for your design.